There has been a trend in recent years to establish so-called "mini mills" or "mini-midi mills". These are mills that typically produce 100,000 to 1,000,000 tons of steel per year as specialized products. These mills have been integrated with continuous casters for casting small billets, bars, and rods. However, the integration of casters and mini mills has not extended to the reduction of slabs to strip thicknesses because of the large capital investment required for floor space and rolling equipment.
This invention relates to an integrated process for the casting and rolling of slabs to form strip and/or sheet. It has particular application to the small steel mill where space is limited. In this process, rolling may take place in a reversing mill rather than a continuous or semi-continuous hot strip mill. It involves the use of continuously cast thin slabs, say on the order of 1.5 inches thick or less. Heretofore, continuous casting has been considered primarily for casting of thick slabs, say 8 inches thick, which slabs must be processed through rolling mills including reheat furnaces, roughing and finishing trains.
In one aspect, this invention relates to unique application of coiler furnaces. The uses of coiler furnaces have been described, for example, in U.S. Pat. Nos. 2,658,741; 4,384,468; 4,430,870; and British Specifications Nos. 918,005 and 652,772.
In yet another aspect, this invention relates to the processing of continuously cast slabs that are as thin as practical, say 1.5 inches or less, as can be coiled. It has been reported that increasingly thinner sections have been cast with present capability limited to about 1 inch thickness, Iron and Steel Engineer, February 1984, p. 47. This article states that government sponsored research is being directed to ultimately casting strip at or near final thickness. However, in the near future, the applicants' approach to thin slab casting and hot rolling almost directly as the slab emerges from caster has much greater potential.